Thunder will shake Wisconsin today and Milwaukee, the state's biggest city, will be at the eye of the storm. I'm not there, and I haven't heard a weather forecast, but I'm confident of my prediction, because Milwaukee is where the Harley-Davidson motorcycle company was born, and this weekend the world's first Harley-Davidson museum opens its doors in the city. Thousands of bikers will roll – or rumble – into town for the opening. When Harley Davidson celebrated its centenary in 2003, upwards of 250,000 riders made the trek to Milwaukee. By all accounts it was loud.

Some of today's riders will arrive in Wisconsin, as I did, on the SS Badger. This lovely old ship ferries passengers, cars and motorcycles the 60 miles across Lake Michigan from Ludington to Manitowoc. The Badger is the last coal-fired steamship sailing in North America. She has been short-cutting passengers from Michigan to Wisconsin across the lake (the drive around is some 400 miles) for more than 50 years. The ship's engines are on the register of national historical monuments.

After boarding, I leaned over the rail to watch a Harley rider lash his bike to the lower deck. (He needn't have bothered, as it turned out: the lake was prairie-flat throughout our crossing.) It seemed amusing that a petrol-head should revert to steam for this part of his journey.

The Badger is an appropriate way to get to Wisconsin, given its nickname, The Badger State. I've always thought of badgers as cuddly creatures, but Magee Johnson, an employee of the ship, explained that they are considered fierce – like a wolverine – in the North Mid-West. She was giving me a tour of the ship's galley, stateroom and viewing decks – in three-inch heels – at the time. "Are Wisconsinites fierce, then?" I asked, as she tottered ahead. "No! They just love beer. And sausages. And cheese. And telling it how it is."

The state's first non-native inhabitants came in the 1820s to dig for lead. Many of them were Cornish miners. Germans, bearing cheese and sausages, subsequently arrived in greater numbers. (There are still more names beginning with "Sch" in Milwaukee's phone directory than there are in Munich's). Cheese won out over lead, and nowadays Wisconsinites happily refer to themselves as "cheeseheads".

Driving north from Manitowoc to Green Bay, Wisconsin's agricultural base was evident. A huge sky loomed over the cultivated plain, which rolled away either side of the freeway. The fields were dotted with clusters of farm buildings; big red barns squatting beneath gun-metal silos, aluminium roofs flashing with sunlight. Yet when I got to Green Bay I saw the state's industrial heritage written in urban sprawl. McDonald's signs on poles two lampposts high, which had punctuated the drive up the freeway, now stood among car lots, cement works and malls.

Happily, Green Bay soon served up a more appealing, individualistic and entrepreneurial side of America. Titletown Brewing Company, a micro-brewery, bar and restaurant situated in a renovated Green Bay railway depot, dates back to 1898. Brewmaster David Oldenbury was keen to demonstrate how he turns mass-production on its head in favour of traditional methods and fresh produce. To begin with, he keeps his cellar upstairs. Hoposaurus Rex made the biggest impression on me (and not because of its daft name). Grapefruit-sharp, yet smooth and worryingly drinkable, it was as far from Miller Lite (produced down in Milwaukee) as beer can get.

"Titletown" is Green Bay's nickname. It refers to the success of the local football (helmets and shoulder-pads) team, the Green Bay Packers, who have won more titles than any other side in the NFL. This is a big deal, made bigger since Green Bay is a comparatively small, remote town. It's as if Truro boasted Manchester United. The state-of-the-art stadium, Lambeau Field, dominates the town much as the cathedral dominates Canterbury.

Grant Turner showed me around. He explained how the Packers are the only NFL team owned by fans, and the only one with season-ticket holders in every state. Grant's father put his name down for a season ticket in 1972, and he finally got one in 1998, a piece of good luck that still makes Grant chuckle today. Some 78,300 people are on the waiting list now; only 50 or 60 are relinquished each year. That said, you can buy a legally touted ticket from a "scalper" for around $200 (£105) if you're keen to see a game, or for $11 (£5.80) you can join the 100,000 or so people who take a stadium tour each year.

Miller Brewing gives a name to one of Lambeau Field's stadium gates. The same is true of the Oneida Nation, a Native American tribe whose reserve – and casino – lies in Green Bay. As at Lambeau Field, you can take a guided tour of the Oneida reserve, a patchwork of land parcels within what once constituted the 65,000 acre Oneida reservation, which the tribe is intent on reclaiming.

I waited for tour guide Kirby Metoxen in the casino. A concrete bear and heron squatted forlornly on rocks in the foyer's fountain; piped muzak washed over us all. This was as close as the tour took me to peace-pipe-and-teepee images of Red Indians. Kirby was keen instead to show me the Oneida's health and day-care centres, the golf-course it wants to buy back from the town, and the houses it has built for its poorer members. The primary school resembles a turtle – central to the tribe's creation myth – but, that aside, Kirby wanted me to think about the Oneida's future as opposed to their past. "I have a pony tail because I like long hair," he told me. "I could cut it off any time if I liked."

There are 11 Native American tribes in Wisconsin – more than in any other state east of the Mississippi. Their languages are dying out (only five people are fluent in Oneida), but a map of the state still rings with their words.

Milwaukee means "gathering place by the water" in Potawatomi. I had preconceptions before I arrived – and all of them turned out to be wrong. I understood that Milwaukee formed part of America's Rust Belt, and that it was a big, formerly industrial, run-down city; I had no idea that it was a vibrant, cultured metropolis, stretching elegantly along the shore of Lake Michigan and around the three rivers which meet within the city limits.

Nowadays Milwaukee has more in common with San Francisco than Detroit. It has Bradford beach – half a mile of clean, powdery sand, in the heart of town – and three other beaches, too. A riverside walk stretches through the city. Old warehouses and new condos line its route. You can still read the advertisements on their huge brick walls, but there's nothing flaky about either the old buildings or the new architecture spliced into the city. The Milwaukee Art Museum, which opened in 2001, looks like Sydney's Opera House crossed with a dragonfly. Santiago Calatrava drew on Frank Lloyd Wright (a Wisconsin native) when he designed the building: it has 217ft louvered sunscreen wings on its roof, which beat twice daily.

I ducked into the Eisner Museum of Advertising and Design in the historic Third Ward. This is the only museum of its kind – skewering consumerism with its own sword – in the USA. Just down the road is the Milwaukee Public Market, a bastion of fresh, local, food. At the West Allis Cheese and Sausage Shoppe Debbie gave me a taste of some of Wisconsin's famous cheeses: Carr Valley Menage, Whiskey Cheese, and Caraway Brick. Bone Suckin' Mustard was also on sale . Up the road in Usinger's, 70 kinds of America's finest gourmet sausages were displayed in a marble-and-tile edifice. I sampled more of Milwaukee's fine slow-food at Roots, a restaurant overlooking the city, run by owner-chef John Raymond. Tiny pots of fried chickpeas and parmesan popcorn set the tone for a stunning meal which ended, for me, with a shot of locally brewed Rehorst Vodka.

The nightlife in Milwaukee is good as well. Festivals take place throughout the summer months; there are hundreds of bars to choose between year round. The Safe House is perhaps the most amusing, and certainly the most discreet. It hides behind a front door stamped "International Exports Ltd". You must whisper in the doorwoman's ear to gain entry. Get the password wrong and she'll make you hop like a monkey or frisk your friend before going in, all of which is secretly filmed and relayed live inside the bar on CCTV. I'd never received a round of applause for entering a bar before. The walls inside are full of spyholes and secret passages and feature chunks of Checkpoint Charlie.

The state of Wisconsin surprised me, and Milwaukee most of all. The bare-headed motorcycle riders (there's no helmet law in Wisconsin) making the pilgrimage into town today know better. I got a sneak preview of their new museum – itself a classic of post-industrial design, perfectly suited to its brown-field site. One of every model Harley Davidson has ever made is on show there, as is Elvis's bike. You can buy and inscribe rivets which the museum will embed in one of its curved, steel display walls.

"Ride it like you stole it" caught my imagination, but the rivet that best fitted the state of Wisconsin read simply, "Life is good".

State lines: Wisconsin

Population 5.4 million
Area eight times the size of Wales
Capital Madison
Date in Union 29 May 1848
Flower Wood Violet
Motto "Forward"
Nickname Badger State

Traveller's Guide

Getting there

The writer flew from Heathrow to Detroit with KLM /NWA (0870 507 4074; www.klm.com), which offers onward connections to Milwaukee.

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